JPH06160205A - Temperature sensor or temperature sensor array composed of glass ceramic and bonded film resistor - Google Patents

Abstract

PURPOSE: To change temperature resistance characteristics of a sensor over a wide range by connecting a parallel resistor of glass ceramics to a film resistor of thin film or thick film and selecting size and constant of the film resistor, so that, within the temperature range for use, the film resistor and the parallel resistor are made to correspond to each other, and below the temperature range, the film resistor is operated, and above the temperature range, the parallel resistor is operated based an its temperature characteristics. CONSTITUTION: A strip-like film resistor 1 of thick film or thin film is sintered on a supporter surface 2 of glass ceramics, and electric connection points 3 are provided on both surfaces. Along the number part of the resistor 1, a parallel resistor 4 of glass ceramics is connected. The resistor 1 is metal or its oxide, and a resistance linearly increases following temperature rising, and the resistance of a resistor 4 exponentially decreases following the temperature rising. By appropriately selecting size and temperature coefficient of the resistor 1, resistance values of the resistors 1 and 4 correspond to each other within usage temperature range. The resistor 1 mainly acts at low temperatures and the resistor 4 at high temperatures. Thus, the temperature resistance characteristics of a sensor circuit can be changed over a wide range.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is particularly suitable for controlling and limiting the power of the glass-ceramic cooking area,
It relates to a temperature sensor or temperature sensor array consisting of a glass ceramic and a bonded film resistor.

[0002]

The use of glass-ceramics as temperature sensors is already known from German patent specification DE 2139828. In this publication, in particular, a temperature measuring resistor (temperature measuring resistor) made of a SiO ₂ —Al ₂ O ₃ —Li ₂ O glass ceramic is described. This glass-ceramic is distinguished by its high resistance to heat shock due to its very low thermal expansion (α is less than 1.5 · 10 ⁻⁶ / K) and therefore very hot industrial furnaces, waste gas chambers. It is particularly suitable as a measurement probe in ,. The publication describes a sensor with the following characteristics for monitoring the temperature of large surfaces. That is, the strip glass-ceramic region is Au, Pt, whose electrical resistance is delimited and whose electrical resistance is used as a temperature-measuring resistor,
Alternatively, it is flatly bonded on the glass-ceramic support with a strip conductor made of Ag. According to this publication, the total resistance of this array is considered to consist of a large number of differential resistor elements connected in parallel, with the minimum resistance occurring when the surface is heated to the maximum. The low thermal conductivity of glass-ceramics prevents the temperature of the overheat point from quickly becoming equal to the surroundings. The total resistance of this array is determined by the resistance of the hottest point on the surface until temperature equalization occurs. Local overheating thus causes, for example, a short-time, extreme resistance change of the temperature-measuring resistor, which is designed as a surface-type used by that publication, and can be used to control overheating protection devices.

US Pat. No. 4,237,368 describes the use of the above sensor to monitor the temperature of the cooking zone of a glass ceramic cooking surface using an electrical comparator. For this purpose, strip-shaped glass-ceramic regions along the diameter of the cooking zone are delimited and, together with two parallel strip conductors made of gold, are coupled to the cooking zone as temperature sensors. The combined strip conductors are bridged by shunt resistors connected in parallel to their outermost ends, resulting in protection of the elements against damage in the cold and hot cooking zones. Each one of the two strip conductors of the temperature sensor is connected to the strip conductor, which strip conductor surrounds the entire cooking surface along its perimeter and functions as a broken glass sensor. German Published Patent Specification No. 3744373A1 describes a power control arrangement and method for a glass-ceramic cooking zone which uses a sensor to determine temperature according to the arrangement of US Pat. No. 4,237,368. In this case, the heat output emitted in each of the cooking zones is controlled as a function of the glass-ceramic temperature and its rate of change. For this purpose, the cooking zone is provided with a strip-shaped glass-ceramic resistance delimited by paralleling gold strip conductors (by changing it in response to temperature changes). An improved power control and monitoring arrangement for a glass-ceramic cooking zone, which in principle corresponds to an arrangement of the above kind with respect to the temperature sensor arrangement of the cooking zone, is German published patent specification DE 374.
It is also known from No. 4372.

The resistivity of all known glass-ceramics used as cooking surfaces is 10 ¹³ at 20 ° C.
Ω · cm to 10 ¹⁵ Ω · cm, temperature is about 20
It reaches 10 ⁷ Ω · cm to 10 ⁹ Ω · cm at 0 ° C. Regardless of the geometrical dimensions of the respective sensor, the temperature measuring signal-or the current or the voltage drop of the sensor at the measuring resistance in series with the sensor-will thus change the temperature range by 10 ⁶ . For the evaluation and subsequent processing of these temperature measurement signals, expensive electronic precision measuring instruments with measuring range switches and / or logarithmic amplifiers are required. Such a device cannot be used in a kitchen stove. This is because a large area, very high resistance sensor placed in the immediate vicinity of the heating coil or cooking zone heating location is sensitive to false signals scattered capacitively or oscillatingly. It is made worse by the fact that additional electrical spending has to be made.

Due to the problems mentioned above, all glass-ceramic temperature sensors described in the "prior art" for controlling and adjusting the cooking zone temperature of glass-ceramic cooking surfaces are unsuitable at temperatures below 200.degree. Is. This is a considerable drawback. Because it keeps hot, melts fat, and in many other applications in the glass-ceramic cooking area, at 200 ° C.
This is because accurate observation of the cooking zone temperature below is necessary and very important to the user. Another disadvantage of the sensors known from the above publication is that they are placed only along the diameter or half-diameter of the cooking zone, respectively, and the low thermal conductivity of the glass-ceramics already mentioned-it is of the order of 2 to 3 W / mK. For some, only the temperatures in these linear partial areas of the cooking zone are to be detected. Thus, sufficient overheating protection of the overall cooking zone is also not guaranteed, nor is the temperature signal provided by the linear partial region with respect to the actual heat flow over the bottom of the pot. Thus, the heating system with the sensor of the above publication is controlled by a temperature signal that does not correspond to the temporary removal of heat from the entire cooking zone.

Other protective temperature limiting devices are also known (for example DE 3705260.8 or DE 3705260.6); this is along the diameter of the cooking zone below the cooking zone. Placed as a separate component at a short distance from the glass-ceramic cooking surface. They are heated by radiant heating elements underneath them as well as by radiation from under the cooking surface. They consist of metal rods with a high thermal expansion placed in a pipe made of a low thermal expansion material. Due to the relative thermal expansion between the metal rod and the pipe, the spring control switch is activated when a certain temperature is reached. This determines the energy timing of the heating element within a narrow temperature range determined by the switching hysteresis of the spring control switch. The temperature control device is a heating element /
Responds to the total temperature of the cooking surface system. Radiant heating of the sides of the cooking surface enters the pot placed above.

The disadvantage of this limiting device arrangement is that here again, the heating of the cooking surface side of the limiting rod is mainly the result of radiant heating of the linear diameter region of the cooking zone placed directly on it. If much heat is taken away from this diameter region, eg the edge region, by the pot above it, the limiting device remains there at a lower temperature than the central region. The limit rod is thus clearly shorter. Because for switching purposes, basically only the hotter central region is now active. Thus, in the case of constant switching characteristics, the switching point and thus the limiting temperature also rises. Due to the non-uniform radiant heating on the side of the cooking surface, the limiting temperature level is thus influenced proportionally to the "active limiting rod length" which becomes effective. If not preferred, this causes overheating of the cooking zone.

The object of the invention is a temperature sensor or temperature sensor array of the type mentioned at the beginning, whose operating temperature range towards relatively low temperatures is much wider than that of a conventional glass-ceramic temperature sensor. Spreading, it is, in contrast to known sensors, to provide a temperature sensor or temperature sensor array which allows reliable monitoring of the temperature of the cooking zone of all heated surfaces, for example glass-ceramic cooking surfaces. In particular, the sensor should be usable as a measuring probe for controlling and limiting the output of the glass-ceramic cooking area.

[0009]

According to the invention, in order to achieve the above-mentioned objects, in particular for controlling and / or limiting the output of the cooking area of glass-ceramics, glass-ceramics and associated film resistors (membranes). resistance)
A temperature sensor or temperature sensor array comprising:
It consists of at least one strip metal or metal oxide thin-film or thick-film resistor designed as a temperature-measuring resistor on a support made of glass-ceramic, which support has electrical connection contacts at both ends and The resistance of glass-ceramic and the parallel circuit are formed, and the temperature resistance characteristics are determined by the superposition of the temperature resistance characteristics of the individual resistors, the resistance values of the individual resistors, and their geometrical dimensions, and at temperatures within the operating temperature range. , The film resistor corresponds to the electrical resistance of the glass-ceramics connected in parallel, so the temperature resistance characteristic of the circuit is determined by the film resistor below this temperature and exponentially decreases with temperature above this temperature. Temperature sensor or temperature sensor characterized by being determined by Sequences are provided. In a preferred embodiment, at least one of the two film resistors attached to each other has electrical connection contacts at both ends and is connected in parallel to the surrounding glass-ceramic to form a measurement circuit almost independent of the attached repetitive circuit. To do. The thin film resistor to be bonded is preferably Au, A
g, Pt, Pd, Au / Ag, Au / Pt, Ag / P
d, or a metal alloy of Au / Pt / Pd.

[0010]

In accordance with the present invention, one or more glass-ceramic resistors are well defined and are associated with a thin film on a surface or special support of glass-ceramic, or with a thick film resistor. . The glass-ceramic resistor together with the film resistor forms a parallel and / or repeating circuit, ie a temperature sensor, as a temperature measuring resistor. The temperature resistance characteristics are determined by the superposition of the temperature resistance characteristics of the individual resistors, the resistance values of the individual resistors, and their geometrical dimensions and circuits. The parallel circuit is in this case formed by a thin-film and / or thick-film resistor with electrical connection contacts at both ends. The film register
As the temperature rises, it is shunted by the resistance of the glass-ceramic placed under and around the film register.

Two opposing or essentially parallel thin film and / or thick film resistors with electrical connection contacts only at one end--as seen as a plurality of resistance cells arranged next to one another Together with the glass-ceramic resistor placed between-forms a repeating circuit. The iterative circuit of the present invention differs from prior art sensors that show a similar design in that the surface resistance of the film resistor associated with the resistance cell is not negligible as would be expected with known sensors. In the above arrangement, the surface resistance according to the present invention is 1 mΩ to 1000Ω / □.
Is. The electrical resistance of all currently known glass-ceramics decreases exponentially with increasing temperature. Law of Rasch and
According to Hinrichsen): lgρ = A + B / T where ρ is the resistivity, A and B are material-specific constants and T is the absolute temperature. For example, FIG. 1 shows SiO ₂ with the constants A = -1.922 and B = 4561.6.
The specific resistance of the suitable glass ceramic for use as -Al ₂ O ₃ -Li ₂ O cooking surface made of a system in which expressed as a function of temperature.

According to the invention, glass-ceramics are suitable as support material because of their low thermal expansion and their resistance to heat shock. However, the invention is in no way limited to the use of glass ceramics. The sensor or sensor array also applies to supports made of comparable materials, such as glass or ceramic. For bonding thin-film or thick-film resistors designed as temperature-measuring resistors, a suitable material is chosen which has a positive temperature coefficient of electrical resistance and therefore the resistance increases linearly with temperature. In special cases, thick film resistors that can be bonded, especially PTC, have a resistance curve to temperature.
Alternatively, it can be made of a material exhibiting NTC characteristics.

As the thin film resistor, a metal resinate which can be used up to a temperature of 800 ° C. and exhibits good electric resistance stability and a good temperature coefficient of electric resistance, and metal alloys Au, A
g, Pt, Pd, Au / Ag, Au / Pt, Ag / Pd
Also, Au / Pt / Pd has been proven to be reliable. Thick film resistors made from the above materials are also used with good temperature coefficient of resistance temperature stability and good temperature coefficient of electrical resistance, but usually at low service temperatures. A film resistor having a high resistance can be formed by using a metal oxide, such as RuO ₂ or R, which also has a positive temperature coefficient.
It is suitably designed as a thick film resistor made from h ₂ O ₃ , IrO ₂ , OsO ₂ , TiO _2, etc. All these materials are applied by screen printing in a manner known to those skilled in the art and baked therein at temperatures of 500 to 1000 ° C.

For production reasons, the sensor register to which one sensor circuit or all sensor circuits are combined consists of a support preferably made of the same material, either all as a thin film resistor or all as a thick film resistor. Designed as a register. However, although more expensive, individual film registers can also be individually designed for special applications. The connection areas of the individual film resistors are preferably reinforced with a silver layer or Ag / Pd or Au, Au / Pt / Pd. They carry suitable contacts, which are glued with a continuous elastic electrically conductive adhesive based on silicone rubber or epoxy resin, or tin solder or tin / indium solder.

[0015]

The advantages obtained with the present invention are, inter alia, the temperature coefficient of the glass-ceramic resistance, by the appropriate selection of the length and width of the thin films and / or resistors to be joined and the thickness of the layers and the temperature coefficient. And the type of sensor circuit (parallel and / or repeating circuit), the temperature resistance characteristics of the sensor circuit can be varied over a wide range to suit the respective measurement problem or the requirements of the control and limiting electronics downstream from the sensor. The geometry and extent of the sensor circuit on the surface whose temperature is to be controlled and / or monitored is almost unrestricted, so that all important areas of the heated surface can be detected. Other advantages and features of the invention include:
It will be more clearly understood from the following description.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the examples shown in the accompanying drawings. FIG. 2 shows, by way of example of a parallel circuit according to the invention, a strip-like thin-film or thick-film resistor (1) which is baked onto a support surface (2) made of glass-ceramic and is provided on both sides with electrical connection contacts (3). ) And an equivalent circuit of this sensor. An electrical resistance (R ₂ ) consisting of a film resistor (R ₁ ) and a glass ceramic (4) located below and along the edge of the film resistor is connected in parallel. The total resistance of this sensor circuit is represented by Equation 1.

[Formula 1]

Given that this parallel circuit is divided into different "cells", the resistances of these cells are connected in series. Thus, the sensor resistance is adjusted to various temperatures that are proportional to the average temperature of the sensor line along the resistor. That is, the individual hotspots are "averaged" by this sensor. For example, to control the temperature of the surface of the cooking zone of the glass-ceramic cooking area, it is desirable to design the film resistor so that the sensor specific temperature resistance is determined only by the basic film resistor. It has a low surface resistance and a material with a positive temperature coefficient of electrical resistance is selected for the film resistor, and its size is determined by the surroundings of the film resistor connected in parallel at the maximum operating temperature of the sensor. It is easily achieved by making it smaller than the electrical resistance of glass ceramics.

FIG. 3 shows a glass-ceramic support having a thickness of 1 mm, a length of 160 mm, and a width of 10 mm, which is baked.
Size 160 × 10mm with surface resistance 0.3Ω / □
The characteristic "A" of such a sensor consisting of ^two film resistors is shown. FIG. 1 shows the dependence of the resistivity of the glass-ceramic support on temperature. The sensors as a whole were heated to their respective temperatures by the temperature scale of Figure 3 (right side of the figure is the resistance scale). A correspondingly designed sensor shows the average temperature of the glass-ceramic cooking surface starting from room temperature and is precisely controlled in the cooking zone area.

The sensor is easily integrated into the cooking surface of the glass-ceramic cooking surface. For this purpose, the film register in the cooking zone area is baked onto the glass-ceramic cooking surface. In order to eliminate localized overheating, in this case the strip-shaped film register is preferably arranged on the cooking surface so that as far as possible all the important areas of the heating surface exposed to the temperature are detected. In particular, the geometry of the film register can be matched to the expected temperature distribution of the practical cooking zone surface. This depends essentially on the type of heating and the geometry and the arrangement of the heat sources, and on the application surface of the overlying pot. In order to keep the interception of the heat flow from the heat source to the cooking surface low, the total surface area of the strip conductors in the cooking zone region in all sensors according to the invention should be at most 10% of the total surface area of the cooking zone.

FIG. 4 is a preferred geometry for the temperature sensor according to the present invention. The sensor is designed as a star (7) with several annular sectors of the cooking zone area (5) of the glass-ceramic cooking area (6). This sensor detects an important partial area of the cooking zone and thus sufficiently prevents overheating of all heated surfaces. This is unattainable with the known linear temperature sensors of the prior art. The average temperature of the cooking zone, for example, is shown and accurately controlled as a function of the temporary removal of heat by the pot above it.

If a material with a high surface resistance, preferably a positive temperature coefficient of resistance, is selected for the film resistor (in some applications a film resistor with a non-linear temperature resistance characteristic is also more suitable). , And if the geometry is made such that the film resistor corresponds to the resistance of the glass-ceramic at temperatures within the temperature range of use, for example at about 480 ° C., then the curve "B" of FIG. As described above, it is possible to obtain a temperature sensor having a temperature resistance characteristic including branches that decrease exponentially at high temperature and increase linearly at low temperature. The data obtained with this temperature sensor is: Thin or thick film register: length 160m
m Width 10 mm Surface resistance 10 Ω / □ Glass-ceramic support and resistance: Length 160 m
m Width 10 mm Thickness 5 mm According to FIG. 1, the specific resistance depends on temperature. The linear increase of the resistance characteristic "B" with temperature corresponds to the increase of the film register;
It is shunted at an accelerated rate due to the resistance of the surrounding glass-ceramic. Its resistance, which decreases exponentially with temperature, is
Only at a higher temperature (from about 349 ° C. in the figure), a remarkable change is shown.

In the cooking zone region incorporated in the glass-ceramic cooking surface, this sensor is similar to the previous embodiment, for example as a star with several annular sectors, and this sensor provides a low cooking surface temperature control of the cooking zone. , Which is used to advantage, and part of the temperature resistance characteristic that decreases rapidly at high temperatures, provides ideal conditions for effective temperature limiting with small switching hysteresis. The location of the reversal of the temperature resistance characteristic within the operating temperature range of the sensor is determined by the magnitude of the surface resistance and the geometrical dimensions of the film resistor. Also, the temperature sensor is basically responsive to the average temperature of the heated surface to be monitored.

FIG. 5 shows, in its simplest form, a repeating network according to the invention. It is formed from two parallel thin film and / or thick film resistors (8) and (9) with an intervening glass ceramic (10). Figure 6
An equivalent circuit of an iterative network is shown. In this equivalent circuit, resistors (R ₁ ) and (R ₂ ) represent the partial circuit of the differential “resistive cell” of the sensor designed as a repeating network. R ₁ is a cumulative resistance consisting of a series connection of two parts of a coupling thin film and / or thick film resistor arranged in a resistance cell. R ₂ represents the glass-ceramic resistance of the cell placed between them. For the total resistance, temperature sensor or R (sensor) of the repeating network, the continuous fraction of equation 2 applies.

[Formula 2] In the above formula 2, R ₁ = R ₁ (θ) R ₂ = R ₂ (θ) and R ₃ = R ₁ + R ₂ or R ₃ (θ) = (R ₁ + R ₂ ) (θ ) Θ = temperature.

If the surface resistance of both film resistors is smaller than the specific resistance of glass-ceramic at the maximum operating temperature of the sensor (R ₁ → 0), the resistance R ₂ is as shown in the equivalent circuit of FIG. , Basically connected in parallel. In this case, the temperature resistance characteristic of the sensor is such that its principle curve matches the curve of the temperature resistance characteristic of the glass ceramic of FIG. When R ₁ << ρ (θ),
The temperature resistance characteristic of the sensor is roughly as follows: R (sensor) (θ) = ρ (θ) M where M is a scale factor determined by the geometrical dimensions of the sensor. A sensor consisting of a repeating circuit with two thin film and / or thick film resistors in parallel, the geometry of the sensor being integrated into the cooking surface of the glass-ceramic cooking area, the sensor consisting of individual film resistors in a parallel circuit. The same guidelines apply as for. The main area of the surface to be monitored must be detected as completely as possible, so this sensor in the cooking zone area is also preferably designed according to FIG. 4 as a star with several annular sectors. . The combined thin or thick film resistors (8) and (9) are shown in FIG.
When designed as a double coil spanning the entire cooking zone (5) of the glass-ceramic cooking area (6), as shown in, the sensor detects almost all hot spots in the cooking zone and It also detects most.

A sensor that controls the temperature of the glass-ceramic cooking surface in the cooking zone region, especially at "low" temperatures (below 200 ° C.) and protects the cooking zone from overheating, consists of two thin and / or thick film resistors in parallel. Designed conveniently. These resistors form a repeating network with the glass-ceramic in between, and one of the two strip-shaped membrane resistors has electrical connecting contacts at both ends. The two membrane resistors provide, on the one hand, an exponential temperature limiting signal whose repetitive network decreases with temperature, and on the other hand, a membrane resistor with its two ends bound giving a signal suitable for temperature control over the entire operating temperature range. Made like. By decoupling temperature control and overheating protection, this arrangement offers the advantage of greater operational safety over simple parallel circuits used for both temperature control and temperature limiting. In particular, the tasks of temperature control and temperature limitation are performed independently of each other by the two electrical switching circuits.

The main circuit of this arrangement can be seen in FIG. The membrane resistors (11) and (12) define the range of glass-ceramic resistance of the repeating network of glass-ceramic surface (13). Film register (1
The area signal is captured in 2). Low resistance film register (1
1) (which preferably represents a linear temperature resistance characteristic with a positive temperature coefficient) is coupled at both ends to provide a control signal proportional to temperature to the resistor (14a). By properly sizing resistors (14) and (14a), the two temperature resistance characteristics of the circuit are significantly independent of each other. If this sensor, located in the cooking zone region of the glass-ceramic cooking surface, is also designed as a star with several annular sectors, it will detect all the important parts of the cooking zone and sufficiently overheat the entire surface. Preventative, average cooking zone temperatures are controlled starting from room temperature in proportion to the heat taken by the pots placed above.

In order to limit the heated glass-ceramic surface temperature as a function of the temperature of the geometrically defined point of the glass-ceramic surface, two connecting thin film and / or thick film resistors of the repeating circuit are actually provided. Basically placed in parallel, but at varying distances from the glass-ceramic surface, the point of minimum distance coincides with the defined temperature measurement point. This temperature sensor provides a signal which is basically a function of the temperature of a particular measuring point. In this case, the measuring point with the highest temperature determines and controls the total resistance of the sensor.

FIG. 9 shows, by way of example in a simple form, the basic arrangement of glass-ceramic baked thin film and / or thick film resistors for such a sensor.
The membrane resistor (15) represented by a simple line and the parallel bent film resistor (16) constitute the closest temperature measuring point. The principle is point a in FIG.
And b with b. With the varying distance between the bend line and the film register drawn as a straight line, a local weighting of the measured point temperature appears. This is shown at D with points c and d in FIG. The local weighting of the individual temperature measuring points can also be achieved in the following way: at least one of the two film resistors arranged one above the other as sinusoids or triangular lines, or specifying the surface to be monitored. Function of
This is achieved by designing the distance from the resistor, which is essentially parallel, as a line determined by the respective temperature distribution.

Experience has shown that the repair of a sensor integrated on the surface to be monitored is not possible in the case of blocking the membrane resistor to be bonded. This is because the original properties of the sensor cannot be restored in this case. For reasons of cost or greater interchangeability of the sensor under greater stress, it is recommended to build the sensor on its own glass-ceramic support away from the heating surface to be monitored. They are then mounted directly below the surface to be monitored, where they are heated by their radiation.

The glass-ceramic support has as a surface:
It can also be designed as a rod with a cross section or as a hollow body. Such a sensor is preferably designed as a "temperature limiting rod". The temperature limiting rod according to the invention consists of a rod-shaped support made of glass ceramic, with a round, oval or rectangular, preferably square cross-section, which rod has a film register , A rectangular cross section is joined to two opposite sides of the whole surface and an oval or round cross section joins the film register along two opposite lines. Thus the limiting rod becomes an iterative circuit. The resistance of a film resistor that is connected in series is conveniently less than the resistance of the support that determines the range at the maximum operating temperature of the sensor over the entire operating temperature range, so the temperature resistance characteristic of the circuit is basically glass. It depends on the temperature of the ceramic. With respect to the repeating circuit, this means that the resistance R ₁ (FIG. 6) is much smaller than the glass-ceramic resistance R ₂ over the temperature range of the limiting rod.

FIG. 10 shows a "temperature limiting rod" (17) for the cooking zone of the glass-ceramic cooking area.
2 shows a sensor designed as and its temperature resistance characteristic. This property applies to rods with the following data: Length of heating zone: 160 mm Cross section: 5 x 10 mm ² Bonding film resistor (18): Surface resistance 3 · 10 on all sides facing each other. ^-3 Ω / □, temperature coefficient of electrical resistance 0.0039 / K.

The rod works with simple switching electronics (eg a comparator) and is attached to the heating element of the cooking zone in the same manner as known protective temperature limiting rods. It is, like the latter, heated both by the radiation of the cooking zone and by the heat generation of the heating elements. Due to the very close parallel circuit of the sensor rod, the total resistance is determined by the smallest resistance of the hottest cell and is almost independent of the position of the hottest spot on the sensor rod. Due to the apparent shortening of the sensor rod when the heat removal varies locally, the movement of the temperature limiting switch point, as seen in prior art rod expansion sensors designed as protective temperature limiting devices, does not occur. Absent.

FIG. 11 shows the conditions for non-uniform heating of the temperature limiting rod S of the present invention. For this purpose, it is assumed that the rod S of its total length 1 takes a temperature of 500 ° C., except for the 1 cm wide region X, while the temperature of the excluded partial region is 600 ° C. The hot partial areas move along the bars as shown in the lower part of FIG. Furthermore, the total resistance R of the sensor and its deviation ΔR are determined by the resistor R _{3 of the} sensor whose temperature is 500 ° C. over the entire length.
Given by. This resistance deviation and the resulting temperature signal deviation are largely independent of the location of the hottest spot.

The geometry and expansion of the sensor circuit on the heated surface depends on the type and geometry of heating and the expected temperature distribution when actually operated. For example, instead of individual sensors extending over a large surface, which are used as measuring elements for temperature limiting, it is often advisable to integrate several small sensors as a sensor array into the surface to be monitored. At the same time, it is possible to measure temperature differences as well as the approximate location of the highest temperature of the heating surface. The low thermal conductivity of glass ceramics of 2 to 3 W / mK in this case improves the thermal decoupling of the individual sensors.

An array of many independent temperature sensors, for example defining a temperature profile along a line, is shown in FIG. This array is baked onto a strip glass-ceramic support. The individual sensors a to f etc. are common to all sensors, basically a bent thin film or thick film resistor, and many strip thin film and / or thick film resistors protruding into a bent "cell". Made of. The sensors are electrically shielded from each other by bending. The temperature resistance characteristics of the individual sensors are determined for each sensor in the array by the geometry of the bend and the size of the surface resistance of the thin film and / or film thickness resistors protruding into the bend individually.

Various examples of possible geometric shapes are shown in FIG.
Can be seen from. Each sensor is fitted with _a potentiometer type resistor (such as T _a to T _f ) and the signal is picked up at S. The temperature sensor is designed again as an iterative network whose signal amplitude depends on the position of the hottest point on the surface detected by the sensor. And the total resistance of both thin film and / or thick film resistors running in parallel is greater per unit length than the electrical resistance of the glass ceramic bound and bound on the glass ceramic support at the maximum operating temperature.

FIG. 13 shows in curves E to G the dependence of the sensor resistance on the position of the 1 cm wide "hot spot". Hotspot is 100K higher than other sensors
Only hot, moving along a sensor designed as a stick. Curves E and F belong to the sensor rod with the following data: Glass-ceramic with the following data: Rod length: 160 mm Rod width: 10 mm Rod thickness: 5 mm Resistivity of the glass ceramic according to FIG. . Combined film register: 160 × 10mm ² , specific resistance 1000Ω
/ □; Temperature coefficient T _k = 0.0039 Ω / K Temperature: Curve E: Hotspot: T ₂ = 500 ° C Other bars: T ₁ = 400 ° C Curve F: Hotspot: T ₂ = 600 ° C Other bars: T ₁ = 500 ° C. In curve G: glass-ceramic as above; surface resistance of resistor to be bonded 100 Ω / □, T _k = 0.003.
9Ω / K Hotspot: T ₂ = 600 ° C, other bars: T ₁ =
500 ° C

The movement of electric current in the glass-ceramic is caused by ionic conduction. In order to avoid polarization phenomena and electrolysis, the sensor should be AC only, preferably 100H.
It should operate at frequencies below z.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship curve with respect to temperature of a specific resistance of a glass ceramic composed of SiO ₂ —Al ₂ O ₃ —Li ₂ O system.

FIG. 2 is a schematic diagram showing an equivalent circuit diagram for a strip-shaped film resistor on a glass-ceramic support forming a parallel circuit diagram with the surrounding glass-ceramic and this arrangement.

FIG. 3 is a graph showing temperature resistance characteristics of two sensors having different designs of individual resistors according to FIG. 2;

4 is a plan view showing the temperature sensor according to FIG. 2 on the surface of the cooking zone of a glass-ceramic cooking surface designed as a star with several circuit sectors.

FIG. 5 is a perspective view showing two parallel thin film and / or thick film resistors that delimit strip glass ceramic resistance as an example of a repeating network structure.

FIG. 6 is an equivalent circuit diagram for the arrangement of FIG.

FIG. 7 is a plan view showing two thin film and / or thick film resistors designed as dual coils, running in parallel in the area of the cooking zone.

FIG. 8 is a schematic diagram showing a temperature sensor consisting of two thin film and / or thick film resistors with electrical connection contacts at three points.

FIG. 9 is an illustration showing an iterative network in which the distances of film registers running in parallel vary locally to weight individual temperature-measuring points.

FIG. 10 is a graph showing a temperature limiting rod according to the present invention and a temperature resistance characteristic thereof.

FIG. 11 is a graph showing changes in the total resistance of the temperature limiting rod during non-uniform heating.

FIG. 12 is a layout showing a sensor arrangement according to the invention for determining a temperature profile along a line.

FIG. 13 is a graph showing a function of the total resistance of a specially constructed repetitive network against the location of “hot spots” on the repetitive network.

[Simple explanation of symbols]

1,8,9,11,12 resistors, 2 support surfaces, 3 electrical connection contacts, 4 glass ceramics, 5 cooking zone areas, 6 glass ceramic cooking areas, 10 glass ceramics, 13 glass ceramic surfaces.

Claims (20)

[Claims] 1. A temperature sensor or temperature sensor array comprising a glass ceramic and an associated film resistor for controlling and / or limiting the output of the cooking area of the glass ceramic, which is made of the glass ceramic. At least one strip-shaped metal or metal oxide thin-film or thick-film resistor designed as a temperature-measuring resistor on a fixed support, which has electrical connection contacts at both ends and the resistance of the surrounding glass-ceramic. And the temperature resistance characteristics are determined by the superposition of the temperature resistance characteristics of the individual resistors, the resistance values of the individual resistors, and their geometrical dimensions. Corresponds to the electrical resistance of the glass-ceramics connected in parallel, and A temperature sensor or temperature sensor array characterized in that the temperature resistance characteristics of the circuit are determined by the film resistor below this temperature and by the glass-ceramic resistance which decreases exponentially with temperature above this temperature. 2. A temperature sensor or temperature sensor array made of glass ceramic and associated film resistors, particularly for controlling and / or limiting the power output in the glass ceramic cooking area, the support being made of glass ceramic. Strip-shaped thin films of metal and / or metal oxide, bounded on one another, bounded on the body and bonded to partial areas of any technically suitable strip-shaped geometric dimension And / or two basically parallel film resistors, which in each case have thick film resistors attached to each other, form a repeating circuit with the electrical resistance of the intervening glass-ceramic, the temperature resistance characteristics of which are Depending on the temperature resistance characteristics of resistors, resistance values of individual resistors and their geometrical arrangement A temperature sensor or temperature sensor array characterized by being determined. 3. Two film resistors so that the resistance of the series-connected coupled film resistors is a function of the position of the "hot spot" on the sensor, at the maximum operating temperature of the sensor, the temperature resistance characteristic of the circuit. 3. The temperature sensor or temperature sensor array of claim 2, limited in range by and greater than the electrical resistance of the glass-ceramics associated therewith per unit length. 4. At least one of the two film resistors attached to each other is provided with electrical connection contacts at both ends and is connected in parallel to the surrounding glass-ceramic to form a measuring circuit almost independent of the attached repetitive circuit. The temperature sensor or temperature sensor array according to claim 2. 5. The resistance of the film resistor, which is connected at both ends in the entire operating temperature range, is lower than the resistance of the surrounding glass ceramic at the maximum operating temperature of the sensor. Therefore, the temperature resistance characteristic of the parallel circuit in the entire operating temperature range of the sensor is basically The temperature sensor or temperature sensor array of claim 4, wherein the temperature sensor is dependent on a film register. 6. For local weighting of temperature measurements,
A film resistor in which the distance between two film resistors attached to each other changes locally, and thus the total resistance of the repeating circuit formed by the two film resistors and the resistance of the intervening glass-ceramic are basically combined. 6. The temperature sensor or temperature sensor array according to any one of claims 2 to 5, depending on the glass-ceramic resistance of the region with the minimum distance of. 7. At least one of the two essentially parallel film registers attached to each other is in a bent shape, or as a sinusoidal or triangular line, or the distance between the registers running parallel to each other. 7. The temperature sensor or temperature sensor array according to claim 6, wherein is designed as a line determined by a function determined by the corresponding temperature distribution of the surface to be monitored. 8. A temperature sensor or temperature sensor array according to claim 1, wherein the film register is baked in a known manner on the surface of the cooking zone of the glass-ceramic cooking area. 9. The shape of the film register on the surface of the cooking zone is matched to the expected temperature distribution of the operating heating surface so that all required areas of the heating surface are detected against thermal stress. 8. A temperature sensor or temperature sensor array according to item 8. 10. A temperature sensor or temperature sensor according to claim 9, wherein the individual film resistors of the parallel circuit on the surface of the cooking zone or the two parallel film resistors of the repeating circuit are designed as a star with several annular sectors. Array. 11. Two of the repeating circuits on the surface of the cooking zone.
10. The temperature sensor or temperature sensor array according to claim 9, wherein the parallel film resistors are designed as a double coil. 12. A support made of glass-ceramic is designed as a bar with an elliptical, circular or rectangular shape, preferably a square cross section, where the bars are two opposed if the cross section is rectangular. 3. A temperature-limiting rod for a glass-ceramic cooking surface, which is connected to the whole surface on the side and to the film register along two opposing lines in the case of an ellipse or a circle in cross section. 7. The temperature sensor or temperature sensor array according to any one of 7 above. 13. The resistance of the coupled film resistors that can be connected in series is lower than the resistance of the limited range support material at the maximum operating temperature of the sensor in the entire operating temperature range, and thus the temperature of the circuit in the entire operating temperature range. 13. The temperature sensor or temperature sensor array of claim 12, wherein the resistance characteristic is essentially determined by the glass ceramic resistance. 14. A plurality of individual thermometric cells, essentially bendable, strip-shaped thin films and / or thicknesses made of metal and / or metal oxide on a support made of glass-ceramic. The range can be determined by the membrane register,
The same temperature resistance characteristics when thin and / or thick film resistors are formed, each having a certain geometric dimension, a certain surface resistance and a temperature coefficient of electrical resistance, and are individually different or have the same cell design. Sensor consisting of glass-ceramic and bonded film resistors, in particular for controlling and limiting the power output of the glass-ceramic cooking area, characterized in that the temperature sensors with the same are formed independently of each other with the bent film resistor. Or a temperature sensor array. 15. The temperature sensor or temperature sensor array according to claim 1, wherein the thin film and / or thick film resistor is made of a material having a positive temperature coefficient of electrical resistance. 16. The thin film resistor to be bonded is Au, A
g, Pt, Pd, Au / Ag, Au / Pt, Ag / P
d or a metal alloy of Au / Pt / Pd.
16. A temperature sensor or temperature sensor array according to any one of claims 1 to 15. 17. The thick film resistor to be bonded is Au, A
g, Pt, Pd, Au / Ag, Au / Pt, Ag / P
d, Au / Pt / Pd, RuO ₂ , Rh ₂ O ₃ , IrO
17. 1 to 16 consisting of ₂ , OsO ₂ or TiO _2.
A temperature sensor or a temperature sensor array according to any one of 1. 18. The sensor film on one or all of the sensor circuits on the support are made of the same material and are made of the same material, all designed as thin film resistors or all designed as thick film resistors. 18. A temperature sensor or temperature sensor array according to any one of 1 to 17. 19. The method according to claim 1, wherein one or all of the sensor circuits on the support, to which the film resistors to which they are attached, consist of supports made of different materials and are designed as thin-film and / or thick-film resistors. 19. The temperature sensor or temperature sensor array according to any one of 18. 20. The film resistors to be combined have Ag, Ag / Pd, Au, Au / P in their connection areas.
20. Any of claims 1 to 19 having electrical contacts reinforced by a layer of t / Pd and bonded to its reinforced connection with tin solder or tin / indium solder or with an epoxy resin based adhesive. The temperature sensor or temperature sensor array of paragraph 1.